Active elements

All the gold compounds used in therapy today (chrysotherapy) are Au(I) compounds (45-47) (10-14). Gold has an intriguing chemistry dominated hy relativistic effects (48) and it is interesting to consider the reasons why Au(III) complexes are not used as anticancer agents like those of Pt(II) are used. 

The acidity of amines is enhanced by more than 30 orders of magnitude when coordinated to Au(III) for example, 

Neither Au(I) nor Au(III) aqua ions, [Au(H20)2] and [Au(H20)4] +, have been characterized in solution or the solid state. The diaqua Au(I) ion is unstable to disproportionation, and stabilization of Au(I) requires TT-acceptor ligands. The dicyano complex K[Au(CN)2], with the characteristic linear two-coordination found in the majority of Au(I) complexes, is very stable and was used with some success to treat tuberculosis at the beginning of the century. Toxic side effects were reduced with thiolate complexes such as aurothiomalate (10), and the French physician Forestier, in 1929, introduced gold(I) thiolates for the treatment of rheumatoid arthritis in the mistaken belief that the two diseases were related 51). 

A variety of injectable gold(I) thiolates (10-13) are now used to treat difficult cases of rheumatoid arthritis and are given in doses of about 25 mg per week for several years. Beneficial effects are often not seen 

The orally active Au(I) complex auranofin (14) has a well-defined, linear two-coordinate structure (64). It is a lipophilic complex, but 

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The addition of cathodically active elements to pure lead was the main objective of investigations to improve its corrosion resistance to H2SO4 [42,44]. Best known is copper-lead with 0.04 to 0.08% Cu. By adding combinations of alloying elements, it was possible to produce lead alloys that not only had much better corrosion resistance, but also had greater high-temperature strength. Lead alloy with 0.1% Sn, 0.1% Cu and 0.1% Pd is an example [45]. 

In many ways the pump is the heart of the lubrication system as it is the only active element. It must furnish sufficient capacity at a high... 

The thermal parameters for comfort should be relatively uniform both spatially and temporally. Variations in heat flow from the body make the physiological temperature regulation more difficult. Nonuniform thermal conditions can lead to nonuniform skin temperatures. The active elements of the regulatory system may need to make more adjustments and work harder in order to keep thermal skin and body temperatures stable. To avoid discomfort from environmental nonuniformities, the temperature difference between feet and head should be less than about 3 °C (Fig. 5.9) and the mean surface temperature or radiant difference from one side of the body to the other should not he greater then about 10 °C. 

A successful start-up requires having in place a comprehensive plan that addresses all aspects of commissioning activities. Elements of such a plan include ... 

J. R. C. Petten, in The role of active elements in the oxidation behaviour of high-temperature metals and alloys. The Netherlands, 12-13 Dec. 1988, ed. Lang, E., Elsevier Applied Science Publishers (1989)... 

Wavefront control function Objective, metrology and active elements... 

The compliance in series with the active force. Force exerted by the activated elements must be transmitted or borne by whatever structural elements are in series with them. In skeletal muscle there is clearly a tendon in series but not so with smooth muscle. In smooth muscle, the total length of contractile apparatus is broken up into individual cells with intercalating extracellular connective structures. In addition, the portions of the crossbridges in series with the pulling site must also be stretched before force can rise to isometric levels. Taken together, the... 

Filling the pores of the support with a solution of the catalytically active element, after which the solvent is removed by drying, is a straightforward way to load a support with active material. However, in this process various interactions are possible between the dissolved catalyst precursor and the surface of the support, which can be used to obtain a good dispersion of the active component over the support. To appreciate the importance of such interactions we need to take a closer look at the surface chemistry of hydroxylated oxides in solution. 

In the past few years, erbium doped materials gained much attention in the field of optical communications, since the Er ion shows a broad optical emission at 1540 nm [111], within the main wavelengths window in the telecommunication technology. For this reason Er can be suitable as an active element for the generation and amplification of light in optical devices [112,113], also if limitations for the realization of an efficient planar amplifier are related to the small cross section for Er excitation (typically 10 -10 cm according to the matrix). In order to enhance Er ion pumping efficiency, a possible... 

The previous chapters are exclusively devoted to the measurements and interpretation of Fe spectra of various iron-containing systems. Iron is, by far, the most extensively explored element in the field of chemistry compared with all other Mdssbauer-active elements because the Mossbauer effect of Fe is very easy to observe and the spectra are, in general, well resolved and they reflect important information about bonding and structural properties. Besides iron, there are a good number of other transition metals suitable for Mossbauer spectroscopy which is, however, less extensively studied because of technical and/or spectral resolution problems. In recent years, many of these difficulties have been overcome, and we shall see in the following sections a good deal of successful Mossbauer spectroscopy that has been performed on compounds of... 

Boltwood BB (1907) Note on a new radio-active element. Amer J Sci 24 370-372... 

Test-tube number Symbol of more active element Symbol of less active element... 

The interaction of electricity with matter was introduced in Chap. 7, where the electrical decomposition of a melted salt was used to prepare active elements from their compounds. An illustration of an electrolysis was shown in Fig. 5-2. Chemical reactions occur at the two electrodes. The electrode at which oxidation occurs is called the anode the one at which reduction takes place is called the cathode. There are two different types of interaction of electricity and matter, as follows ... 

Many other elements affect the electrochemical activity of aluminum even at a trace (ppm) level. Thus, copper, zinc, and iron are found to counteract the effect of the activating elements. So... 

The physiologically active elements are anatomical or histological elements, which are the real and simplest carriers of the simplest known vital properties. So Bernard draws a clear borderline between chemistry and histology. Life is bound to histology as to its proximate condition. 

In phase-fluorimetric oxygen sensors, active elements are excited with periodically modulated light, and changes in fluorescence phase characteristics are measured. The delay or emission (phase shift, ( ), measured in degrees angle) relates to the lifetime of the dye (x) and oxygen concentration as follows ... 

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